Syria was suspended from the Arab League in 2011 after cracking down on protests against the regime.
After previous attempts to send aid have been blocked, an aid convoy has made it to earthquake-ravaged northwestern Syria.
Rustam Azhiev, better known by his nom-de-guerre Abdul Hakim al-Shishani, led Ajnad al-Kavkaz in Syria and now leads Chechen fighters in the Ukrainian Foreign Legion.
The way was paved last year through meetings between the security chiefs of the countries, whose rapprochement had seemed unthinkable.